1991 Johnson 70hp quit and won't restart

[25-06shooter]

I have read some of the other topics and can't find exactly this problem, so here goes.

I took the pontoon out yesterday for the first time in about 5 months and ran around the cove at the boat landing for about 5 minutes at half throttle. I stopped in the middle of the lake to answer the phone and left the motor idling. It quit and wouldn't restart. I have checked the plugs and all have a good blue spark. It is getting plenty of gas, to the point of almost flooding. It seems like 1 cylinder will fire every 3 or 4 revolutions. I am at a loss to find the problem. The only thing I did different this time is fill the tank with high-test gas because it won't be run for another 2 or 3 months.

Any ideas?

Thanks in advance for the help,

Nate

 

[kenmyfam]

Re: 1991 Johnson 70hp quit and won't restart

Basic health check to begin with.

Compression
Spark (checked with a spark tester and a half inch gap)
Fuel delivery
Spark plug condition.

Post results and go from there.
Welcome to iboats

 

[Home Cookin']

Re: 1991 Johnson 70hp quit and won't restart

sounds like water in the gas to me. Try running off a different tank.

 

[kenmyfam]

Re: 1991 Johnson 70hp quit and won't restart

Is the gas 5 months old with no stabilizer ????

 

[25-06shooter]

Re: 1991 Johnson 70hp quit and won't restart

The compression is 80 to 90 psi on all 3 cylinders.
I have at least a half inch of spark on the tester.
The spark plugs look fine, they are relatively new, I've cleaned them and they throw a good blue flame.
I changed out the fuel, used regular gas, mixed, drained the bowls, cleared the fuel line, pumped up the fuel (you can hear the fuel filling the bowls easily), and tried again. Still the same.
You can wind on the starter and it will hit every few revolutions, but as soon as you let off the key it will either backfire or fire 1 time.

If it was an old vehicle I would say check the timing, but I don't know enough about boat motors to know where to start.

Thanks again,

Nate

 

[billy4hp]

Re: 1991 Johnson 70hp quit and won't restart

The compression is 80 to 90 psi on all 3 cylinders.I have at least a half inch of spark on the tester.
The spark plugs look fine, they are relatively new, I've cleaned them and they throw a good blue flame.
I changed out the fuel, used regular gas, mixed, drained the bowls, cleared the fuel line, pumped up the fuel (you can hear the fuel filling the bowls easily), and tried again. Still the same.
You can wind on the starter and it will hit every few revolutions, but as soon as you let off the key it will either backfire or fire 1 time.

If it was an old vehicle I would say check the timing, but I don't know enough about boat motors to know where to start.

Thanks again,

Nate

Not to throw an alarm, and I don't believe it is keeping it from running. But those compression numbers seem quite a bit low, depending on how you are achieving them.

But for comparison's sake my 1978 70hp with a strong battery makes 125 to 130 psi... Now if your doing your compression test by rope pull method or if your battery is weak this could cause much lower numbers...

Now for your main issue, it needs a spark for every compression stroke and your indicating one every 3 or 4 rotations, sounds like an electronic / ignition issue. Do you have a OEM service manual for your model year engine? If not, I highly recommend getting one as it will save you countless hours of guessing and there misdiagnosing your engine. They can be found on Ebay and Ken Cook's books...

JMHO

 

[kenmyfam]

Re: 1991 Johnson 70hp quit and won't restart

Are the plugs wet ??? and if so do the smell strongly of gas ??
Compression testers vary. I would not worry about that right at this moment. Get it running and give it a decarb then check compression again.
Did you read about ethanol poisoning in the top secret files ???
Is it cranking as fast as it usually does ??? You need 300 rpm + to fire it up if I remember correctly.

 

[bktheking]

Re: 1991 Johnson 70hp quit and won't restart

Read the following:

http://www.cdielectronics.com/downl... 1979-2001 60-75 HP (Without Quick-Start).pdf

 

[ezeke]

Re: 1991 Johnson 70hp quit and won't restart

I have read some of the other topics and can't find exactly this problem, so here goes.

I took the pontoon out yesterday for the first time in about 5 months and ran around the cove at the boat landing for about 5 minutes at half throttle. I stopped in the middle of the lake to answer the phone and left the motor idling. It quit and wouldn't restart. I have checked the plugs and all have a good blue spark. It is getting plenty of gas, to the point of almost flooding. It seems like 1 cylinder will fire every 3 or 4 revolutions. I am at a loss to find the problem. The only thing I did different this time is fill the tank with high-test gas because it won't be run for another 2 or 3 months.

Any ideas?

Thanks in advance for the help,

Nate

Maybe it is flooding. Check the primer solenoid to be sure that it is functioning properly.

You might also want to check to be sure that the flywheel is torqued to specification if anyone has worked on the ignition recently.

 

[25-06shooter]

Re: 1991 Johnson 70hp quit and won't restart

The flywheel evidently was not torqued the last time it was off. The nut came off relatively easy. I put the puller on it last night and tightened it up, but it is stuck pretty good, so I think it might have sheared the keyway, which will put it out of time. We'll see if it has popped loose when I get home this evening.

What should the torque be on the flyweel bolt?

Thanks for all the help,

Nate

 

[ezeke]

Re: 1991 Johnson 70hp quit and won't restart

The flywheel evidently was not torqued the last time it was off. The nut came off relatively easy. I put the puller on it last night and tightened it up, but it is stuck pretty good, so I think it might have sheared the keyway, which will put it out of time. We'll see if it has popped loose when I get home this evening.

What should the torque be on the flyweel bolt?

Thanks for all the help,

Nate

100 to 105 foot pounds. Be sure to use a OEM key, the timing depends on it.